Hi Reed sorry to hear things aren't so good. Firstly, regardless of your wife's b.s. you should find out if this guy really is a paedophile. If my friends had kids or grandchildren around this guy, I would want to know exactly what he did before I could make decision on him. Google can help you find any papers or news reports written about it at the time. I don't know about the US but in the UK you can request a list of SO's in your area.

Finding out just how much of a threat this guy is and making sure that if he is , assuming this isn't some elaborate lie your ex made up, that any friends or family with children are informed in sensible way, allowing them access to the relevant information.